<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 变量</h1>
<p id="demo"></p>
<script>
var price1 = 7;
var price2 = 8;
var price3 = 12;
var total = price1 + price2 + price3;
document.getElementById("demo").innerHTML = "总计：" + total;
</script>
</body>
</html>